Cathode ray tube (CRT) displays, such as those commonly used in desk-top computer screens, function as a result of a scanning electron beam from an electron gun, impinging on phosphors on a relatively distant screen. The electrons increase the energy level of the phosphors. When the phosphors return to their normal energy level, they release the energy from the electrons as a photon of light, which is transmitted through the glass screen of the display to the viewer. One disadvantage of a CRT is the depth of the display required to accommodate the raster scanner.
Flat panel displays have become increasingly important in appliances requiring lightweight portable screens. Currently, such screens use electroluminescent or liquid crystal technology. Another promising technology is the use of a matrix-addressable array of cold cathode emission devices to excite phosphor on a screen, often referred to as a field emitter display.
Spindt, et. al. discuss field emission cathode structures in U.S. Pat. Nos. 3,665,241, and 3,755,704, and 3,812,559. To produce the desired field emission, a potential source is provided with its positive terminal connected to the gate, or grid, and its negative terminal connected to the emitter electrode (cathode conductor substrate). The potential source is variable for the purpose of controlling the electron emission current.
Upon application of a potential between the electrodes, an electric field is established between the emitter tips and the low potential anode grid, thus causing electrons to be emitted from the cathode tips through the holes in the grid electrode.
The clarity, or resolution, of a field emission display is a function of a number of factors, including emitter tip sharpness, alignment and spacing of the gates, or grid openings, which surround the tips, pixel size, as well as cathode-to-gate and cathode-to-screen voltages. These factors are also interrelated. For example, the voltage required for electron emission from the emitter tips is a function of both cathode-to-gate spacing and tip sharpness.